A Syrian army helicopter dropped two barrel bombs on a refugee camp in the northern province of Idlib, residents say, with footage posted on YouTube showing charred and dismembered bodies.

The footage showed corpses of women, children and burning tents while people scrambled to save the wounded.

"It's a massacre of refugees," a voice off camera said.

"Let the whole world see this, they are displaced people. Look at them, they are civilians, displaced civilians."

A man in another video of the Abedin camp, which houses people fleeing the fighting in neighbouring Hama province, said as many as 75 people had died.

The British-based Syrian Observatory for Human Rights, which supports those opposing Syrian president Bashar al-Assad, said 10 civilians died.

There was no mention of the bombing on Syrian state media.

Reuters could not independently confirm the attack.

One video shows a man arriving at the scene on a motorbike.

He runs into the camp and screams at others to pick up the bodies, trying to convince them that the people on the ground with limbs missing might still survive if taken to hospital.

"This one's good! This one's good!" he shouts, telling two men to carry a limp body to a nearby pick-up truck.

"Pick him up from the stomach not the leg," he screams.

US 'horrified' by reports of attack

The United States said it was "horrified" by the reports, calling the attack "barbaric."

"We are horrified by the reports that the Assad regime barrel bombed the Abedin displaced persons camp in Idlib and the images we saw of the carnage against innocent civilians," state department spokeswoman Jen Psaki said.

"The attack on the Abedin camp was nothing short of barbaric."

Ms Psaki said the US could not confirm details of the incident, but said if the bombings proved to have been carried out by Mr Assad's forces, "it is only the latest act of brutality by the regime against its own people."